import java.util.Scanner;

public class Main1643 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        double a= sc.nextDouble();
        double x=20;
        if (a<=x){
            System.out.println(String.format("%.2f",a*1.68));
        }else if (a>x){
            System.out.println(String.format("%.2f",a*1.98));
        }
    }
}
